1. Field of the Invention
The present invention is broadly concerned with new methods of synthesis of polyepoxysuccinic acid (PESA), as well as derivatives and analogs thereof and copolymers including PESA moieties or repeat units. More particularly, the invention is concerned with such synthesis methods which completely eliminate the need for calcium-bearing compounds, thus allowing the synthesis without the need for costly and difficult removal of calcium.
2. Description of the Prior Art
In industrial cooling systems, water from rivers, lakes, or ponds is employed as cooling media for evaporative heat exchangers. Such natural waters contain large amounts of suspended materials, such as silt, clay, organic wastes, and dissolved salts (e.g., calcium and magnesium), and often, such contaminants can settle out as scale on the heat exchangers and related equipment, resulting in decreased efficiencies. In addition, during recovery and transfer of crude petroleum products, accompanying waters, sometimes even more contaminated than surface waters, can create severe scale and corrosion problems in well and transfer equipment.
PESA has been used in the past as an effective green corrosion and scale inhibitor, and also as dispersants for calcium carbonate, calcium sulfate, calcium fluoride, silica scale, and related compounds. PESA is traditionally prepared by polymerizing epoxysuccinic acid (ESA) with Ca+2 ion, typically through the use of calcium hydroxide. Such synthesis techniques have been described in numerous patents, see, e.g., U.S. Pat. Nos. 4,065,475, 4,654,159, and 5,062,962. A drawback of these techniques is that the initial polymerized reaction product requires the removal of calcium via ion exchange resins, and only the homo-polymer PESA can be prepared. These purification steps significantly increase the costs associated with PESA production, and the homo-polymer limitation effectively excludes production of polymers including ESA repeat units with other repeat units such as acrylates.
There is accordingly a need in the art for improved PESA synthesis methods which eliminate the need for calcium ion, thereby reducing the production costs, while at the same time permitting co-polymerization with ESA and other repeat units.